Monoclonal gammopathy of renal significance (MGRS) is characterized by kidney damage caused by monoclonal Ig that is secreted by a B cell or plasma cell clone not meeting diagnostic criteria for multiple myeloma or a lymphoproliferative disorder. All pathological findings associated with the clonal expansion of Ig-secreting cells can be seen in both myeloma and MGRS. The underlying pathology is likely determined by the characteristics of the secreted protein. Entities associated with MGRS include proliferative glomerulonephritis with monoclonal Ig deposits (PGNMID), C3 glomerulopathy with monoclonal gammopathy, AL amyloid, type 1 cryoglobulinemia, fibrillary glomerulonephritis, and immunotactoid glomerulopathy.
Kidney manifestations of MGRS are usually caused by deposition of monoclonal Ig light chains. Patients can present with both nephrotic and subnephrotic proteinuria, hematuria, and elevated serum creatinine.
Kidney biopsy is necessary to make the diagnosis. In addition to evaluating for underlying myeloma and chronic lymphocytic leukemia, further testing may include serum and urine protein electrophoresis, immunofixation, measurement of free light chains, and bone marrow biopsy. Because treatment is aimed at eradication of the expanded clonal line, it is important that the care of patients with MGRS be coordinated with a myeloma specialist.
This is a recently defined set of kidney disorders found in patients who would otherwise meet the criteria for monoclonal gammopathy of undetermined significance but have an abnormal urinalysis and kidney insufficiency. This patient who otherwise meets the diagnostic criteria for monoclonal gammopathy of undetermined significance has an active urine sediment and an increase in the serum creatinine level and thus has underlying kidney disease. MGRS is an increasingly recognized disorder, and a kidney biopsy is necessary to make the diagnosis by demonstrating the presence of monoclonal immunoglobulin deposition in the kidney. MGRS can affect the kidney in various ways, including amyloidosis, proliferative glomerulonephritis, immunoglobulin deposition disease, C3 glomerulopathy, and proximal tubulopathy. Kidney manifestations of MGRS are usually caused by deposition of monoclonal light chains. Patients can present with both nephrotic and subnephrotic proteinuria, hematuria, and elevated serum creatinine. Despite not meeting the definition of multiple myeloma, MGRS increases morbidity and, in most cases, should be treated with therapy designed to eliminate or suppress the immunoglobulin clone.